Chromatography system

ABSTRACT

A chromatography system includes a modulator, a chromatograph, a cooler, and a detector. The chromatograph is connected to the modulator by a first heated transfer line. The detector is connected to the modulator by a second heated transfer line. The cooler is connected to the modulator. The modulator is arranged outside of the chromatograph.

TECHNICAL FIELD

This disclosure relates to a chromatography system.

BACKGROUND

Existing chromatography systems and methods perform adequately for theirintended purpose. However, improvements to such systems and methods arecontinuously being sought in order to advance the arts.

SUMMARY

One aspect of the disclosure provides a chromatography system includinga modulator, a chromatograph, a cooler and a detector. The chromatographis connected to the modulator by a first heated transfer line. Thedetector is connected to the modulator by a second heated transfer line.The cooler is connected to the modulator and the modulator is arrangedoutside of the chromatograph.

Implementations of the disclosure may include one or more of thefollowing optional features. In some implementations, the modulator maybe provided together with a secondary oven, where the modulator isconnected to the first heated transfer line. The secondary oven isconnected to the second heated transfer line.

In some implementations, the gas chromatography system includes a heatpipe or a thermosiphon system that connects the modulator with thecooler. The heat pipe or the thermosiphon system is configured to removeheat from the modulator. Alternatively, in other implementations, thecooler is disposed on the modulator.

In some examples, the secondary oven includes a cylindrical shape.Additionally, the secondary oven may include a cylindrical ceramicheater.

In some implementations, the modulator includes a heater and a capillarycolumn defining a void. The capillary column arranged in the void of theheater.

In some examples, the modulator is connected to the heat pipe or athermosiphon system, and the heater is in direct contact with the heatpipe or the thermosiphon system. In some examples, the heater may bedisposed on a surface of the capillary column. While, in other examples,the heater defines a heater thickness having the surface disposed on thecapillary column. In this case, the heater includes a heating elementdisposed on the surface of the heater or within a threshold distancefrom the surface of the heater.

In some examples, the capillary column may be in direct contact with theheater. The heater may be a ceramic heater. In some examples, thechromatography system further includes insulation disposed upon theheater. The insulation may be layered. Additionally or alternatively,the insulation may be a vacuum insulated covering.

The heater may include a thermal conducting material. In someimplementations, the thermal conducting material is aluminum nitride.The heater may include a temperature sensor. In some examples, theheater includes two or more stages.

In some examples, the modulator defines a first heating zone and asecond heating zone adjacent to the first heating zone. At a firstperiod of time, the first and second heating zones are not heated. Forexample, at the first period of time, the first and second heating zonesmay be cooled. At a second period of time following the first period oftime, the first heating zone is heated causing samples to pass from acapillary column within the heated transfer line to the capillary columnwithin the second heating zone passing through the first heating zone.At a third period of time following the second period of time, the firstheating zone is not heated preventing samples from passing from thecapillary column within the heated transfer line to the capillary columnwithin the second heating zone. For example, at the third period oftime, the first heating zone may be cooled. Finally, at a fourth periodof time following the third period of time, the second heating zone isheated causing samples to pass from the capillary column within thesecond heating zone to the capillary column within the secondary oven.

In some implementations, the first heated line is configured to transfera sample from the chromatograph to the modulator. The second heated lineis configured to transfer the sample from the modulator to the detectorthrough the second heated transfer line. In some implementations, thefirst transfer line transfers a sample to the modulator. The modulatorreceives the sample and transfers the sample to the secondary oven,which in turn transfers the sample to the second transfer line.

In some examples, the cooler is a Stirling cooler. In addition, the heatpipe or the thermosiphon system removes heat from the modulator, morespecifically the modulator.

In some implementations, the chromatography system includes a secondaryoven. The modulator is positioned within the secondary oven. Thesecondary oven is connected to the first heated transfer line and thesecond heated transfer line.

In some examples, the chromatograph is a gas chromatograph. In otherexamples, the chromatograph is a two-dimensional gas chromatograph.

The details of one or more implementations of the disclosure are setforth in the accompanying drawings and the description below. Otheraspects, features, and advantages will be apparent from the descriptionand drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of an exemplary gas chromatography system.

FIG. 2 is a schematic view of an exemplary modulator-secondary oven ofthe gas chromatography system of FIG. 1.

FIG. 3A is a side view of an exemplary modulator portion of themodulator-secondary oven of the gas chromatography system of FIG. 1connected to a cooler of the gas chromatography system of FIG. 1.

FIG. 3B is a cross-sectional view of the modulator portion according toline 3-3 of FIG. 3A.

FIG. 4A is a side view of an exemplary modulator portion of themodulator-secondary oven of the gas chromatography system of FIG. 1connected to a cooler of the gas chromatography system of FIG. 1.

FIG. 4B is a cross-sectional view of the modulator portion according toline 4-4 of FIG. 4A.

FIG. 5A is a side view of an exemplary modulator portion of themodulator-secondary oven of the gas chromatography system of FIG. 1connected to a cooler of the gas chromatography system of FIG. 1.

FIG. 5B is a cross-sectional view of the modulator portion according toline 5-5 of FIG. 5A.

FIG. 5C is a cross-sectional view of the modulator portion according toline 5-5 of FIG. 5A.

FIG. 6 is a view of an exemplary heating sequence of a two-zone heaterof an exemplary modulator portion of the modulator-secondary oven of thegas chromatography system of FIG. 1.

FIG. 7 is a view of an exemplary heating sequence of a three-zone heaterof an exemplary modulator portion of the modulator-secondary oven of thegas chromatography system of FIG. 1.

FIG. 8 is a view of an exemplary heating sequence of a seven-zone heaterof an exemplary modulator portion of the modulator-secondary oven of thegas chromatography system of FIG. 1.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure describes an exemplary system having a chromatograph anda modulator, and more specifically a comprehensive two-dimensional gaschromatography (“GC×GC”) system with a thermal modulator. In someimplementations, a two-dimensional gas chromatography system includes athermal modulator that: (1) produces sufficiently narrow reinjectionbands for optimum comprehensive two-dimensional gas chromatography, (2)provides fast modulation, (3) may require only electricity foroperation, (4) operates with standard capillary gas chromatographiccolumns (“capillary GC columns”), and (5) allows easy installation ofthe standard capillary GC column.

FIG. 1 shows, a block diagram of an exemplary system 10. The system 10includes a modulator-secondary oven 12, a chromatograph, such as a gaschromatograph (“GC”) 14, a cooler 16 (e.g., a cryogenic cooler or othertypes of coolers), and a detector 18. A first heated transfer line 20connects the modulator-secondary oven 12 to the GC 14. A second heatedtransfer line 22 connects the modulator-secondary oven 12 to thedetector 18. A heat pipe or a thermosiphon system 24 connects themodulator-secondary oven 12 to the cooler 16. As will be explained inmore detail below, the configuration of the system 10 may allow forsuccessful trapping of volatile compounds at higher temperatures thanwould otherwise be possible.

While a modulator-secondary oven assembly 12 is described as a preferredembodiment, it is to be understood by the ordinary artisan that thesecondary oven 12 may be omitted such that a secondary oven should notbe read into the claims unless express reference is made therein to asecondary oven. For brevity, however, the remainder of the disclosurerefers to a modulator-secondary oven assembly 12.

With continued reference now to FIG. 1, in an implementation, amodulator-secondary oven assembly 12 is arranged outside of the gaschromatograph 14. As shown, modulator-secondary oven assembly 12 isarranged between the GC 14 and the mass spectrometer 18. In someexamples, the modulator-secondary oven assembly 12 is positioned on topof the GC 14 in a substantially similar manner to a valve oven.

In an implementation, a sample (not shown) is transferred through thefirst heated transfer line 20 from the gas chromatograph 14 to themodulator-secondary oven 12. The sample may be further transferred fromthe modulator-secondary oven 12 to the detector 18 (or other externalgas chromatographic detectors, not shown) through the second heatedtransfer line 22.

In a preferred embodiment, an arrangement of the modulator-secondaryoven 12 outside of the gas chromatograph 14, as opposed to the currentdesigns where the modulator is positioned inside the GC oven, providesseveral advantages. Some of the advantages may include, but are notlimited to: (1) temperatures of the modulator-secondary oven 12 belowthe temperature of the GC oven are more easily achieved and controlled,(2) temperatures of the modulator-secondary oven 12 are more easily andbetter controlled outside of the turbulent air flow within the GC oven,(3) the position of the modulator-secondary oven 12 outside of the GCoven frees up space in the GC oven (that is already relatively small),and does not disturb air flow and temperature within the GC oven, and(4) the modulator-secondary oven 12 may be positioned relatively closerto the detector 18 with a relatively shorter second heated transfer line22, which may benefit fast chromatography in the second dimension.

The cooler 16 may be a cryogenic cooler, which produces narrowerreinjection bands. Additionally, the cryogenic cooler 16 may be aStirling cooler in order to reach cryogenic temperatures. Inimplementations, a Stirling cooler usually includes (from a first end toa second end) a piston, a compression space, and heat exchanger (all atan ambient temperature), a regenerator, and a heat exchanger, expansionspace, and a piston (all at a lower temperature). Referring to FIG. 2,the heat pipe or the thermosiphon system 24 is situated to remove heatfrom the modulator 12 a to the cooler 16 such that the cooler 16 doesnot have to be connected directly to the modulator 12 a. However, insome implementations, the cooler 16 may be connected directly tomodulator 12 a (not shown). Other coolers 16, such as, but not limitedto low-temperature refrigeration and thermoelectric coolers may beimplemented with different modulator designs to address the temperaturedifferences of the coolers 16. In general, cryogenic temperatures(˜−150° C. and colder) provide better modulation (i.e. narrowerreinjection bands) presumably because of steeper temperature gradients.However, with longer modulator zones (described below) and bettercontrolled heating and temperature gradients, narrower reinjection bandsare expected to be possible at higher temperatures. A reinjection bandcan be defined as the sample reinjected into the secondary oven 12 bafter it goes through the modulator 12 a.

In some examples, the detector 18 is a mass spectrometer, such as, forexample, a time-of-flight mass spectrometer.

FIG. 2 is a block diagram of an exemplary modulator-secondary ovenassembly 12. The modulator-secondary oven 12 can includes a modulatorportion 12 a connected to a secondary oven portion 12 b. The modulatorportion 12 a is connected to the first heated transfer line 20. Thesecondary oven portion 12 b is connected to the second heated transferline 22. In some instances, the design of the secondary oven portion 12b may include a cylindrical shape and may be, for example, a cylindricalceramic heater into which the capillary GC column is wound. In otherexamples, the secondary oven portion 12 b may include other shapes, suchas, but not limited to a square shape or a rectangular shape. In someinstances (not shown), the modulator 12 a may be located within thesecondary oven 12 b.

The exemplary modulator-secondary oven 12 of FIG. 2 may be an integrateddesign such that the capillary GC column 28 (shown in FIG. 3A) isreadily installed and that the path for the sample transition from themodulator portion 12 a to the secondary oven portion 12 b is integral tothe assembly to facilitate a narrow reinjection band. Considerations forthe design of the exemplary modulator-secondary oven 12 of FIG. 2include, but are not limited to: (1) the temperature transitions (e.g.,uniform temperature, no hot or cold spots) to and from the first andsecond transfer lines 20, 22, (2) uniform temperature transition fromthe modulator portion 12 a to the secondary oven portion 12 b, (3)temperature gradient of hot-to-cold in going from the modulator portion12 a to the secondary oven portion 12 b to maintain the narrowreinjection band, (4) minimal capillary GC column connections, and (5)minimal steps and manipulations of the capillary GC column forinstallation. In some implementations, for capillary GC column 28installation, the steps may include: (1) disposing the capillary GCcolumn 28 in the second transfer line 22 of the mass spectrometer 18,(2) winding the capillary GC column 28 into the secondary oven portion12 b, (3) sliding the capillary GC column 28 through the modulatorportion 12 a or laying the capillary GC column 28 into the modulatorportion 12 a, (4) sliding the capillary GC column 28 through the firsttransfer line 20 to the GC 14, (5) closing a cover (see, e.g., 30 inFIGS. 3B, 4A, 4B) on the exemplary modulator-secondary oven 12, and (6)connecting a primary column (not shown) and a secondary column in the GCoven 14. The primary column is included in the GC oven 14 and thesecondary column connects to the primary column in the GC oven andextends through the modulator-secondary oven 12 and the detector 18. Theprimary and secondary columns form the capillary GC column 28.

FIGS. 3A, 4A and 5A illustrate exemplary modulator portions 12 a ₁, 12 a₂, 12 a ₃ connected to the heat pipe or the thermosiphon system 24. Eachof the exemplary modulator portions 12 a ₁, 12 a ₂, 12 a ₃ include: (1)a heater 26 (e.g., a ceramic heater, or any fast heating, low thermalmass heater) in direct contact with the heat pipe or the thermosiphonsystem 24 for cooling the heater 26 and capillary GC column 28 and (2)the capillary GC column 28 in direct contact with the heater 26. Inother words, the heater 26 defines a void that houses the capillary GCcolumn 28. The attachment of the heater 26 to the cooling source, i.e.,the heat pipe or the thermosiphon system 24 provides good thermalconduction to the capillary GC column 28 (which transfers the sample).

Insulation 30 may be disposed upon one or both of the modulation portion12 a of the heat pipe or the thermosiphon system 24 (FIG. 3A) and theheater 26 (FIG. 4A), which may facilitate a reduction or elimination ofcondensation of frost thereon. In some examples, the insulation 30 maybe a layered type of insulation material used in cryogenics. In otherexamples, the insulation 30 may be a vacuum insulated covering orcontainer.

Referring to FIGS. 3A and 3B, in some examples, the heat pipe or thethermosiphon system 24 may define a hole that is configured to receivethe heater 26. In addition, as previously described, the heater 26 maydefine a void for housing the capillary GC column 28. As shown, theinsulation 30 is disposed about the heat pipe or the thermosiphon system24 within the modulation portion 12 a.

Referring to FIGS. 4A and 4B, in some examples, the heat pipe or thethermosiphon system 24 define a semi-circular shape having an openportion configured to receive the heater 26. Similar to FIGS. 3A and 3B,the heater 26 defines a void for housing the capillary GC column 28. Insuch implementation, the insulation 30 may be disposed over the heater26 to thereby form a semi-circular shape that is complementary to thesemi-circular shape of the heat pipe or the thermosiphon system 24.

Referring to FIGS. 5A, 5B, and 5C, in some implementation, a heatingelement 32 may be positioned within or on the surface of the heater 26.For example, the heater 26 may define a thickness T having a surface incontact with the capillary column 28. The heating element 32, may bepositioned anywhere within the thickness T or on the surface of theheater 26. Referring to FIG. 5B, the heat pipe or the thermosiphonsystem 24 may have a flat surface on which the heater 26 is closelyattached to the heat pipe or the thermosiphon system 24, while in FIG.5C, the heat pipe or the thermosiphon system 24 has a U-shape, whichalso allows for a closely attached surface between the heater 26 and theheat pipe or the thermosiphon system 24.

Referring back to FIGS. 3A, 4A, and 5A, in some instances, the heater 26of the exemplary modulator portions 12 a ₁, 12 a ₂, 12 a ₃ may include agood thermal conducting material (e.g., aluminum nitride). Furthermore,the heater 26 may include a fast responding temperature sensor (notshown). In other examples, the heater 26 is arranged close to thesurface of the capillary column 28 or even on the surface of thecapillary column 28 in a substantially similar manner as thick filmheaters. The heater 26 may include at least two stages (in asubstantially similar manner as two-stage thermal modulators) ormultiple heater zones for complex heating sequences as discussed ingreater detail below. The heater 26 may also be defined by varying wattdensities along its (axial to column) length and/or varying thickness ofsubstrate separating the heater 26 from the capillary column 28 tocreate temperature gradients to focus the reinjection bands. In mostinstances, the exemplary modulator portions 12 a ₁, 12 a ₂, 12 a ₃ mayhave two stages or pseudo two stages to separate the reinjection bandfrom the incoming primary column effluent. A stage is a portion orsection of the modulator 12 a which is configured to trap and reinject asample. In a two stage modulator 12 a, the sample is trapped from theprimary column of the first transfer line 20 in the first stage and thenreinjected to the second stage where the sample is trapped andreinjected into the column in the secondary-oven 12 b. The purpose oftwo stages is to separate the sample band cleanly from the sample thatis flowing continuously from the primary column of the first transferline 20. The first stage holds the sample while the second stagereinjects the portion trapped in the previous modulation. Heater zones(described below with respect to FIGS. 6-8) are separately controlled,adjacent, contiguous portions on a single heater structure 26. Thesezones are then controlled in some fashion that is either a one stage ortwo stage modulator 12 a, or a pseudo two stage when operated as apseudo heat wave.

Referring to FIGS. 6, 7 and 8, exemplary individual heating zones alongthe length of the modulator portion 12 a along a heater 26 are shown inorder to illustrate exemplary heating sequences. In most instances, thecooling is in direct contact with the heater 26, and, the capillarycolumn 28 is: (1) in contact with heater 26 (e.g., a ceramic heater, orany fast heating, low thermal mass heater) or (2) near the heater 26.The heating and cooling should be fast enough to achieve a minimummodulation period of approximately 1 second, while a minimum modulationperiod of approximately 0.5 seconds may be desirable. Someconsiderations that may be taken into account when designing the heater26 may include, but are not limited to: (1) the length of each zone, (2)the number of zones, (3) the speed of heating and cooling of the heater26, and, thus, the capillary column 28, (4) the placement of a heatingelement 32 (see, e.g., FIGS. 5B, 5C) within or on the surface of theceramic substrate of the heater 26, (5) varying watt density within azone or from zone-to-zone, (6) varying substrate thickness between theheating element 32 and the column, (7) varying substrate thicknessbetween the heating element 32 and the cooling source, (8) the thermaleffect of the leads connected to the heating element 32 (which may be asource of cold spots), and (9) timing of the heating sequence of thezones. For example, at cryogenic trapping temperatures (e.g., 150 to 200deg C. below the elution temperature of an analyte), the length of theheating zone(s) may be between one millimeter and ten millimeters. Attemperatures higher than cryogenic trapping temperatures, the length ofthe heating zone(s) may be between one centimeter and ten centimeters.At temperatures lower than cryogenic trapping temperatures, the lengthof the heating zone(s) may be less than one centimeter.

Referring to FIG. 6, an exemplary heating sequence of a two-zone heater26 along the length of the modulator portion 12 a is shown and will nowbe described. For clarity, the term cooling as used in the descriptioncan mean an active cooling or it may mean a reduction/withdrawal of heatsuch that such reduction/withdrawal of heat has a net cooling effect.

In some instances, the exemplary configuration illustrated in FIG. 6 maybe analogous to a two-stage, quad-jet modulator. Initially as shown instep A, both zones of the heater 26 are cooled and the sample comingfrom the primary column of the GC 14 is trapped at the entrance to themodulator portion 12 a. At step B, the first zone is heated to move thesample from the first zone to the second zone and then, at step C, thefirst zone is cooled to stop the sample coming from the primary column.Finally, at step D, the second zone is heated to reinject the sampleinto the secondary column and then the modulator portion 12 a returns tothe initial state by turning off the second zone (i.e., by cooling thesecond zone). Depending on many parameters (e.g., temperature gradientsbetween zones, speed of heating and cooling, speed of modulation, flowvelocity, analyte volatility), the exemplary configuration associatedwith the exemplary heating sequence of a two-zone heater 26 may or maynot work well. Expected challenges may include moving the samplecompletely from the first stage to the second stage while also making aclean cut of the sample from the primary column effluent and thenreinjecting a sharp band from the second stage while not having anytailing from slower moving sample caught between the stages.Accordingly, the exemplary heating sequence of a two-zone heater 26 maylikely require specially designed temperature gradients controlled bysubstrate thickness and heater watt densities axially along thecapillary column 28.

Referring to FIG. 7, an exemplary heating sequence of a three-zoneheater 26 is shown; in some instances, this exemplary configuration mayprovide a possible solution to ill-defined temperature regions betweenzones 1 and 2 of the above-described two-zone heater configuration ofFIG. 6. However, a design configuration including a three-zone heater 26may still suffer from an ill-defined temperature zone between the firstand second zones; although this may be controlled by timing, the controlmay depend on: (1) the temperature gradients between zones, (2) howquickly the system heats and cools, (3) flow velocity, and (4) thevolatility of analytes. As shown, the heating sequence defines threezones along the length of the modulator portion 12 a. At step A,initially, the three zones of the heater 26 are cooled and the samplecoming from the primary column is trapped at the entrance to themodulator portion 12 a. At step B, the first and second zones are heatedto move the sample from the first zone to the second zone. At step C,the first zone is cooled to stop the sample coming from the primarycolumn. At step D, the third zone is heated to reinject the sample intothe secondary column, and then at step E, the second and third zones arecooled, which results in the modulator portion 12 a returning to theinitial state.

Referring to FIG. 8, an exemplary heating sequence for a multiple (e.g.,seven) zone heater 26 is shown. Although a seven zone heater is shown inFIG. 8, the number of zones can vary depending on the properties of theheating and cooling. In a configuration including a multiple-zone heater26, the heating sequence is a pseudo heat wave that moves from theentrance of the modulator portion 12 a to the exit of the modulatorportion 12 a in a substantially similar manner as that in a mechanicalmodulator, which may be a “sweeper” having a heated arm that rotatesover the column, moving the trapped sample along the column in front ofthe hot arm. As shown, the heating sequence defines seven zones alongthe length of the modulator portion 12 a. At step A, initially, theseven zones of the heater 26 are cooled and the sample coming from theprimary column (not shown) is trapped in the at the entrance to themodulator portion 12 a. At step B, the first and second zones are heatedto move the sample from the first zone to the third zone. At step C, thefirst zone is cooled to stop the sample coming from the primary columnand the third zone is heated to move the sample to the fourth zone. Atstep D, the second zone is cooled and the fourth zone heated to move thesample to the fifth zone. At step E, the third zone is cooled and thefifth zone is heated to move the sample to the sixth zone. At step F,the fourth zone is cooled and sixth zone is heated to move the sample tothe seventh zone. Finally, at step G, the fifth zone is cooled and theseventh zone is heated to reinject the sample into a portion of thecolumn 28 located in the secondary oven 12 (i.e., a portion of thesecondary column), and then the sixth and seventh zones are cooled,which results in the modulator portion 12 a returning to the initialstate.

As seen in FIG. 8, two zones are heated at a time, and, the two zonesheated move one zone at a time. Heating two zones at a time may bebetter than heating one zone at a time because the area of thetemperature gradient between zones should be heated better while movingfrom zone-to-zone. Depending on: (1) the heating and cooling properties,(2) the length of the zones, (3) the period of the modulation, (4) theflow velocity, and (5) the volatility of analytes, more zones may betterseparate the reinjection sample from the trapped sample of the primarycolumn. The timing may be important for focusing and separating thereinjection band from the effluent of the primary column. The “heatwave” must not travel faster than the sample transport through thecapillary column 28 within the modulator portion 12 a. If the heating issufficiently high that the sample is essentially unretained, the samplemay travel at the velocity of the carrier gas. The “heat wave” must movemore slowly than the velocity of the carrier gas. The slower the “heatwave” moves, the more the sample is moved from the temperature gradientzone and the better the separation of the reinjection zone is from theprimary column effluent. However, if the “heat wave” moves too slowly,the modulation period may be longer than the minimum required modulationperiod. Also, if the “heat wave” moves too slowly the sample maybreakthrough the cold zone behind the “heat wave”.

By having multiple zones, it is expected that the “heat wave” can movequickly and better separate the reinjection band from the trappedprimary column effluent. This should reduce or eliminate peak tailing inthe reinjection band. To adjust for different modulation periods, thefinal step could be a hold. Also, the steeper the temperature gradientbetween a heated and cooled zone, the better the focusing of thereinjection band. Steeper gradients should be achieved by lowertemperatures.

A closer examination of conditions for modulation includes typical flowvelocities and how fast the sample moves through the modulator portion12 a when heated sufficiently to be unretained. For typical columndiameters and column lengths, the flow velocity may be approximately 100cm/sec to approximately 400 cm/sec (or approximately 0.1 cm/ms toapproximately 0.4 cm/ms) in the modulator portion 12 a. It is probablynot possible to heat fast enough to move the wave faster than thisvelocity if the length of a heater zone is 1 cm. This means the speed ofthe “heat wave” is limited by how fast the heating is. If the heater is10 zones, a 0.5 second modulation period divided by 10 zones is 0.05seconds per zone. This would require heating at least 150 degreesCelsius in this time period or 3000 degrees per second. This may not bepossible. Heating at least 150 degrees Celsius above the trappingtemperature is typically considered the rise in temperature needed toremobilize (reinject) a sample when the sample is trapped at asufficiently low temperature. Conversely, the modulator 12 a needs to becooled about 150 degrees Celsius below the temperature at which thesample (analyte) elutes from the primary column in the GC oven 14. Thenfor reinjection, the temperature of the modulator 12 a needs to beraised to about 150 degrees Celsius. So ideally, the temperaturedifferential between the modulator trapping temperature and the GC oventemperature is controlled to be at or around 150 degrees Celsius as theGC oven 14 temperature rises. For example analyte A elutes from theprimary column in the GC oven 14 at 50 degrees Celsius, so the modulator12 a may trap it at ˜−100 degrees Celsius (150° C. lower) and thenreinject it at about 50 degrees Celsius. While analyte B elutes laterfrom the primary column in the GC oven 14 at 300 degrees Celsius, so themodulator 12 a traps it at 150 degrees Celsius (150 degrees Celsiuslower) and reinjects it at 300 degrees Celsius. Note that these areapproximate numbers.

One ceramic heater manufacturer claims a heating rate of approximately1,400 degrees per second. If 1,500 degrees per second is achievable,then the time to heat 150° is 0.1 seconds. For a 0.5 second modulationperiod, only five zones would be possible. For a 1 second modulationperiod, 10 zones would be possible. For the sequence in FIG. 8, sevenzones would work for a 0.6 second modulation period because the firststep heats two zones. A 1.0 second modulation period would be sufficientfor a column set with a 30 m×0.25 mm primary column and helium carriergas. As far as speed of heating, the smaller the heater (and each zone),the faster the heating. If a smaller heater is needed for heating speed,a lower trapping temperature may be needed because the lower thetemperature, the better the trapping and the shorter the length of eachheater zone that is required.

Other parameters to consider are the trapping temperature (i.e., thetemperature at which the movement of the sample through the modulator issignificantly slowed or essentially stopped) and breakthrough (i.e., thesample moving through the modulator and out of the modulator during thetrapping step because of insufficient trapping). These parametersdetermine (i) how fast the heat wave has to move before the samplebreaks through and (ii) the maximum modulation period. The heat waveshould stay ahead of, or move faster than, the trapped sample. Thisspeed along with the length of each zone and how many zones may limithow long the modulation period can be. Unless the trapping temperatureis extremely cold (e.g., less than −150 degrees Celsius), the sample mayhave some measurable movement through the trapping zone over a length oftime of a typical modulation period, and the speed of movement maydepend on the trapping temperature. The higher the trapping temperature,the faster the trapped sample moves. Either each zone must be longer,or, the number of zones must be greater, or, a combination of the two.The length of the trapping zone may determine how long the sample can beheld before breaking through and exiting the trapping zone. A longermodulator (trapping zone) may be required for higher trappingtemperatures.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. Accordingly, otherimplementations are within the scope of the following claims. Forexample, the actions recited in the claims can be performed in adifferent order and still achieve desirable results.

What is claimed is:
 1. A chromatography system comprising: a modulator;a chromatograph connected to the modulator by a first heated transferline; a detector connected to the modulator by a second heated transferline; a cooler connected to the modulator, wherein the modulator isarranged outside of the chromatograph; a secondary oven connected to themodulator, wherein the modulator is connected to the first heatedtransfer line, and the secondary oven is connected to the second heatedtransfer line; and a heat pipe or a thermosiphon system connecting themodulator with the cooler, the heat pipe or the thermosiphon systemconfigured to remove heat from the modulator.
 2. The chromatographysystem according to claim 1, wherein the secondary oven includes acylindrical shape.
 3. The chromatography system according to claim 2,wherein the secondary oven includes a cylindrical ceramic heater.
 4. Thechromatography system according to claim 1, wherein the modulatorcomprises: a heater defining a void; and a capillary column arranged inthe void of the heater.
 5. The chromatography system according to claim4, wherein the heater is in direct contact with the heat pipe or thethermosiphon system.
 6. The chromatography system according to claim 4,wherein the heater is disposed on a surface of the capillary column. 7.The chromatography system according to claim 4, wherein the heaterdefines a heater thickness having a surface disposed on the capillarycolumn, the heater comprising a heating element disposed on the surfaceof the heater or within a threshold distance from the surface of theheater.
 8. The chromatography system according to claim 4, wherein thecapillary column is in direct contact with the heater.
 9. Thechromatography system according to claim 4, wherein the heater is aceramic heater.
 10. The chromatography system according to claim 4,further comprising insulation disposed upon the heater.
 11. Thechromatography system according to claim 10, wherein the insulation islayered.
 12. The chromatography system according to claim 10, whereinthe insulation is a vacuum insulated covering.
 13. The chromatographysystem according to claim 4, wherein the heater includes a thermalconducting material.
 14. The chromatography system according to claim13, wherein the thermal conducting material is aluminum nitride.
 15. Thechromatography system according to claim 4, wherein the heater includestwo or more stages.
 16. The chromatography system according to claim 1,wherein the first heated transfer line is configured to transfer asample from the chromatograph to the modulator, and wherein the secondheated transfer line is configured to transfer the sample from themodulator to the detector.
 17. The chromatography system according toclaim 1, wherein the cooler is a Stirling cooler.
 18. The chromatographysystem according to claim 1, wherein the modulator is positioned withinthe secondary oven.
 19. The chromatography system according to claim 1,wherein the chromatograph is a gas chromatograph.